David beat me to my own thought process. So I will stay away from that and I give you:

The inner sleeve artwork as Tarkus progresses is just as good.

How I wish this could have happened:

Before settling on Carl Palmer, who at that time was a member of Atomic Rooster, they approached Mitch Mitchell of The Jimi Hendrix Experience. Emerson and Lake were uninterested in Mitchell, however, as he showed up for a 'jam' session with an arsenal of guns and unruly bodyguards. Hendrix, tired of his band and wanting to try something different, expressed an interest in playing with the group. Since Emerson and Lake had settled on Palmer by then, this led the British press to speculate about a supergroup called HELP, or "Hendrix, Emerson, Lake & Palmer".[2] Because of scheduling conflicts, such plans were not immediately realised, but the initial three planned a jam session with Hendrix after their second concert at the Isle of Wight Festival (their debut being in The Guildhall, Plymouth, on 23 August 1970, with the band "Earth" as support), with the possibility of him joining. Hendrix died 26 days later, and the three pressed on as Emerson, Lake and Palmer.

Greg Lake made this comment on ELP's discussions with Hendrix:

"Yeah, that story is indeed true, to some degree...Mitch Mitchell had told Jimi about us and he said he wanted to explore the idea. Even after Mitch was long out of the picture and we had already settled on Carl, talk about working with Jimi continued. We were supposed to get together and jam with him around August or September of 1970, but he died before we could put it together."